#include<stdio.h>
void swap1(int x,int y),swap2(int *px,int *py),swap3(int *px,int*py);
int main(void)
{
	int a=1,b=2;
	int*pa=&a,*pb=&b;
	
	swap1(a,b);
	printf("after calling swap1: a=%d b=%d\n",a,b);
	
	a=1;b=2;
	
	swap2(pa,pb);
	 printf("after calling swap2: a=%d b=%d\n",a,b);
	 
	 a=1;b=2;
	 swap3(pa,pb);
	  printf("after calling swap3: a=%d b=%d\n",a,b);
	  return 0;
}
  void swap1(int x,int y){
	int t;
	t=x;
	x=y;
  	y=t;
}
void swap2(int*px,int*py){
	int t;
	t=*px;
	*px=*py;
  	*py=t;
}
void swap3(int*px,int*py){
	int *pt;
	pt=px;
	px=py;
  	py=pt;
}
